Android:如何从Kotlin调用ndk函数? [英] Android: How to call ndk function from Kotlin?

问题描述

此代码在Java上有效.但是在迁移到Kotlin之后，编译器将方法native fun stringFromNative(): String视为错误，并显示以下文本:

This code works on Java. But after migration to Kotlin, compiler higlits method native fun stringFromNative(): String as error with following text:

没有主体的功能必须是抽象的

Function without a body must be abstract

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    Toast.makeText(this, stringFromNative(), Toast.LENGTH_LONG).show()
}

companion object {

    init {
        System.loadLibrary("_ndkkt")
    }
    native fun stringFromNative(): String
}
}

感谢@KenVanHoeylandt！

Thanks @KenVanHoeylandt!

Andswer是:

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    Toast.makeText(this, stringFromNative(), Toast.LENGTH_LONG).show()
}

   init {
        System.loadLibrary("_ndkkt")
    }

    external fun getStringFromNative(): String
}

}

如果您希望在另一个类中使用此本机函数，则可以指定将其封闭的类，如下所示:

If you wish to use this native function in another class you can specify the class which encloses it as in:

val aStringFromNative : String = MainActivity().getStringFromNative()

推荐答案

将external fun stringFromNative(): String放在同伴对象之外，并放入MainActivity.

Put external fun stringFromNative(): String outside of the companion object and into the MainActivity.

(我通过查看 https://github.com/ligee/kotlin-找到了答案ndk-samples )

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